System and method for non-contact electronic articulation sensing

ABSTRACT

A surgical instrument is disclosed. The instrument includes a handle portion, a body portion extending distally from the handle portion and defining a first longitudinal axis and an articulating tool assembly defining a second longitudinal axis and having a proximal end. The articulating tool assembly is disposed at a distal end of the body portion and is movable from a first position in which the second longitudinal axis is substantially aligned with the first longitudinal axis to at least a second position in which the second longitudinal axis is disposed at an angle with respect to the first longitudinal axis. The instrument also includes an articulation mechanism configured to articulate the articulating tool assembly, the articulation mechanism including an articulation sensor assembly configured to transmit a sensor signal to a microcontroller which is configured to determine an articulation angle of the articulation assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 14/459,008, filed on Aug. 13, 2014, which is adivisional application of U.S. application Ser. No. 12/942,292, filed onNov. 9, 2010, now U.S. Pat. No. 8,807,414, which claims the benefit ofand priority to U.S. Provisional Application Ser. No. 61/285,014, filedon Dec. 9, 2009, and which is a continuation-in-part application of U.S.application Ser. No. 12/345,167, filed on Dec. 29, 2008, now U.S. Pat.No. 7,815,090, which is a continuation application of U.S. applicationSer. No. 11/544,203, filed on Oct. 6, 2006, now U.S. Pat. No. 7,481,348,and which is a continuation-in-part of U.S. application Ser. No.12/189,834, filed on Aug. 12, 2008, now abandoned, which claims priorityto U.S. Provisional Application Ser. No. 60/997,854, filed on Oct. 5,2007, the entire contents of all of which are hereby incorporated byreference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to a surgical instrument having anarticulating tool assembly. More particularly, the present disclosurerelates to a surgical instrument which includes a mechanism foractuating an articulating surgical instrument, e.g., a linear stapler,from a non-articulated position, wherein the mechanism includes anarticulation sensor assembly.

2. Background of Related Art

Surgical instruments which include a tool assembly mounted on a distalend of a body portion of the surgical instrument for articulation arewell known. Typically, such surgical instruments include articulationcontrol mechanisms which allow an operator to remotely articulate thetool assembly in relation to the body portion of a surgical instrumentto allow the operator to more easily access, operate on, and/ormanipulate tissue.

Such articulating tool assemblies have become desirable, especially inthe endoscopic surgical procedures. In an endoscopic surgical procedure,the distal end of a surgical instrument is inserted through smallincisions in the body to access a surgical site. Typically, anappropriately sized cannula, e.g., 5 mm, 10 mm, etc., is insertedthrough the body incision to provide a guide channel for accessing thesurgical site.

Current known devices can typically require 10-60 pounds of manual handforce to clamp tissue and deploy and form surgical fasteners in tissuewhich, over repeated use, can cause a surgeon's hand to become fatigued.Gas powered pneumatic staplers which implant surgical fasteners intotissue are known in the art. Certain of these instruments utilize apressurized gas supply which connects to a trigger mechanism. Thetrigger mechanism, when depressed, simply releases pressurized gas toimplant a fastener into tissue.

Motor-powered surgical staplers are also known in the art. These includepowered surgical staplers having motors which activate staple firingmechanisms. However, these motor powered devices only provide forlimited user control of the stapling process. The user can only toggle asingle switch and/or button to actuate the motor and appliescorresponding torque to the stapler's firing mechanisms. In certainother devices, a controller is used to control the stapler.

There is a continual need for new and improved powered surgical staplerswhich include various sensors. The sensors provide relevant feedback tofeedback controllers which automatically adjust various parameters ofthe powered stapler in response to sensed feedback signalsrepresentative of stapler operation, including articulation andactuation of the tool assemblies.

SUMMARY

According to one aspect of the present disclosure, a surgical instrumentis disclosed. The instrument includes a handle portion, a body portionextending distally from the handle portion and defining a firstlongitudinal axis and an articulating tool assembly defining a secondlongitudinal axis and having a proximal end. The articulating toolassembly is disposed at a distal end of the body portion and is movablefrom a first position in which the second longitudinal axis issubstantially aligned with the first longitudinal axis to at least asecond position in which the second longitudinal axis is disposed at anangle with respect to the first longitudinal axis. The instrument alsoincludes an articulation mechanism configured to articulate thearticulating tool assembly, the articulation mechanism including anarticulation sensor assembly configured to transmit a sensor signal to amicrocontroller which is configured to determine an articulation angleof the articulation assembly.

According to another aspect of the present disclosure, a surgicalinstrument is disclosed. The instrument includes a handle portion, abody portion extending distally from the handle portion and defining afirst longitudinal axis and an articulating tool assembly defining asecond longitudinal axis and having a proximal end. The articulatingtool assembly is disposed at a distal end of the body portion and ismovable from a first position in which the second longitudinal axis issubstantially aligned with the first longitudinal axis to at least asecond position in which the second longitudinal axis is disposed at anangle with respect to the first longitudinal axis. The instrument alsoincludes an articulation mechanism configured to articulate thearticulating tool assembly. The articulation mechanism includes ahousing block configured to receive an articulation spindle rotatablyhoused therein, an articulation link operatively coupled to thearticulation spindle, an articulation knob coupled to the articulationspindle for rotating the articulation spindle, wherein rotational motionof the articulation knob is translated into axial motion of thearticulation link thereby articulating the articulating surgical toolassembly and an articulation sensor assembly configured to transmit asensor signal to a microcontroller which is configured to determine anarticulation angle of the articulation assembly.

According to another aspect of the present disclosure, an articulationmechanism configured to articulate an articulating tool assembly isdisclosed. The articulating tool assembly is disposed at a distal end ofthe body portion and is movable from a first position in which thesecond longitudinal axis is substantially aligned with the firstlongitudinal axis to at least a second position in which the secondlongitudinal axis is disposed at an angle with respect to the firstlongitudinal axis. The articulation mechanism includes a housing blockconfigured to receive an articulation spindle rotatably housed therein,an articulation link operatively coupled to the articulation spindle andan articulation knob coupled to the articulation spindle for rotatingthe articulation spindle, wherein rotational motion of the articulationknob is translated into axial motion of the articulation link therebyarticulating the articulating surgical tool assembly. The articulationmechanism also includes an articulation sensor assembly configured totransmit a sensor signal to a microcontroller which is configured todetermine an articulation angle of the articulation assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1 is a perspective view of a powered surgical instrument accordingto an embodiment of the present disclosure;

FIG. 2 is a partial enlarged perspective view of the powered surgicalinstrument according to the embodiment of the present disclosure of FIG.1;

FIG. 3 is a partial enlarged plan view of the powered surgicalinstrument according to the embodiment of the present disclosure of FIG.1;

FIG. 4 is a partial perspective sectional view of internal components ofthe powered surgical instrument of FIG. 1 in accordance with anembodiment of the present disclosure;

FIG. 5 is a partial perspective view of an articulation mechanism of thepowered surgical instrument of FIG. 1 in accordance with an embodimentof the present disclosure;

FIG. 6 is a partial perspective sectional view of the articulationmechanism of FIG. 5 in accordance with an embodiment of the presentdisclosure;

FIG. 7 is a partial side sectional view of the articulation mechanism ofFIG. 5 in accordance with an embodiment of the present disclosure;

FIG. 8 is a partial top sectional view of the articulation mechanism ofFIG. 5 in accordance with an embodiment of the present disclosure;

FIG. 9 is a partial bottom sectional view of the articulation mechanismof FIG. 5 in accordance with an embodiment of the present disclosure;

FIG. 10 is a partial side sectional view of the articulation mechanismof FIG. 5 in accordance with an embodiment of the present disclosure;and

FIG. 11 is a partial side sectional view of the articulation mechanismof FIG. 5 in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the presently disclosed powered surgical instrument arenow described in detail with reference to the drawings, in which likereference numerals designate identical or corresponding elements in eachof the several views. As used herein the term “distal” refers to thatportion of the powered surgical instrument, or component thereof,farther from the user while the term “proximal” refers to that portionof the powered surgical instrument or component thereof, closer to theuser.

A powered surgical instrument, e.g., a surgical stapler, in accordancewith the present disclosure is referred to in the figures as referencenumeral 10. Referring initially to FIG. 1, powered surgical instrument10 includes a housing 110, an endoscopic portion 140 defining a firstlongitudinal axis A-A extending therethrough, and an articulating toolassembly (e.g., end effector 160), defining a second longitudinal axisB-B extending therethrough. Endoscopic portion 140 extends distally fromhousing 110 and the end effector 160 is disposed adjacent a distalportion of endoscopic portion 140. In an embodiment, the components ofthe housing 110 are sealed against infiltration of particulate and/orfluid contamination and help prevent damage of the components bysterilization processes.

According to an embodiment of the present disclosure, end effector 160includes a first jaw member having one or more surgical fasteners (e.g.,cartridge assembly 164) and a second opposing jaw member including ananvil portion for deploying and forming the surgical fasteners (e.g., ananvil assembly 162). In certain embodiments, the staples are housed incartridge assembly 164 to apply linear rows of staples to body tissueeither in simultaneous or sequential manner. Either one or both of theanvil assembly 162 and the cartridge assembly 164 are movable inrelation to one another between an open position, in which the anvilassembly 162 is spaced from cartridge assembly 164, and an approximatedor clamped position, in which the anvil assembly 162 is in juxtaposedalignment with cartridge assembly 164.

It is further envisioned that end effector 160 is attached to a mountingportion 166, which is pivotably attached to a body portion 168. Bodyportion 168 may be integral with endoscopic portion 140 of poweredsurgical instrument 10, or may be removably attached to the instrument10 to provide a replaceable, disposable loading unit (DLU) or single useloading unit (SULU) (e.g., loading unit 169). In certain embodiments,the reusable portion may be configured for sterilization and re-use in asubsequent surgical procedure.

The loading unit 169 may be connectable to endoscopic portion 140through a bayonet connection. It is envisioned that the loading unit 169has an articulation link connected to mounting portion 166 of theloading unit 169 and the articulation link is connected to a linkage rodso that the end effector 160 is articulated as the linkage rod istranslated in the distal-proximal direction along first longitudinalaxis A-A as discussed in more detail below. Other means of connectingend effector 160 to endoscopic portion 140 to allow articulation may beused, such as a flexible tube or a tube comprising a plurality ofpivotable members.

The loading unit 169 may incorporate or be configured to incorporatevarious end effectors, such as vessel sealing devices, linear staplingdevices, circular stapling devices, cutters, graspers, etc. Such endeffectors may be coupled to endoscopic portion 140 of powered surgicalinstrument 10. An intermediate flexible shaft may be included betweenhandle portion 112 and loading unit. It is envisioned that theincorporation of a flexible shaft may facilitate access to and/or withincertain areas of the body.

With reference to FIGS. 1 and 2, an enlarged view of the housing 110 isillustrated according to an embodiment of the present disclosure. In theillustrated embodiment, housing 110 includes a handle portion 112 havinga main drive switch 114 disposed thereon. The switch 114 may includefirst and second switches 114 a and 114 b formed together as a toggleswitch. The handle portion 112, which defines a handle axis H-H, isconfigured to be grasped by fingers of a user. The handle portion 112has an ergonomic shape providing ample palm grip leverage which helpsprevent the handle portion 112 from being squeezed out of the user'shand during operation. Each switch 114 a and 114 b is shown as beingdisposed at a suitable location on handle portion 112 to facilitate itsdepression by a user's finger or fingers.

Additionally, and with reference to FIGS. 1 and 2, switches 114 a, 114 bmay be used for starting and/or stopping movement of drive motor 200(FIG. 4). In one embodiment, the switch 114 a is configured to activatethe drive motor 200 in a first direction to advance firing rod (notexplicitly shown) in a distal direction thereby approximating the anviland the cartridge assemblies 162 and 164. Conversely, the switch 114 bmay be configured to retract the firing rod to open the anvil andcartridge assemblies 162 and 164 by activating the drive motor 200 in areverse direction. The retraction mode initiates a mechanical lock out,preventing further progression of stapling and cutting by the loadingunit 169. The toggle has a first position for activating switch 114 a, asecond position for activating switch 114 b, and a neutral positionbetween the first and second positions.

The housing 110, in particular the handle portion 112, includes switchshields 117 a and 117 b. The switch shields 117 a and 117 b may have arib-like shape surrounding the bottom portion of the switch 114 a andthe top portion of the switch 114 b, respectively. The switch shield 117a and 117 b prevent accidental activation of the switch 114. Further,the switches 114 a and 114 b have high tactile feedback requiringincreased pressure for activation.

In one embodiment, the switches 114 a and 114 b are configured asmulti-speed (e.g., two or more), incremental or variable speed switcheswhich control the speed of the drive motor 200 and the firing rod in anon-linear manner. For example, switches 114 a, 114 b can bepressure-sensitive. This type of control interface allows for gradualincrease in the rate of speed of the drive components from a slower andmore precise mode to a faster operation. To prevent accidentalactivation of retraction, the switch 114 b may be disconnectedelectronically until a fail safe switch 114 c is pressed.

The switches 114 a and 114 b are coupled to a non-linear speed controlcircuit which can be implemented as a voltage regulation circuit, avariable resistance circuit, or a microelectronic pulse width modulationcircuit. The switches 114 a and 144 b may interface with the controlcircuit by displacing or actuating variable control devices, such asrheostatic devices, multiple position switch circuit, linear and/orrotary variable displacement transducers, linear and/or rotarypotentiometers, optical encoders, ferromagnetic sensors, and Hall Effectsensors. This allows the switches 114 a and 114 b to operate the drivemotor 200 in multiple speed modes, such as gradually increasing thespeed of the drive motor 200 either incrementally or gradually dependingon the type of the control circuit being used, based on the depressionof the switches 114 a and 114 b.

FIGS. 2-4 illustrate an articulation mechanism 170, including anarticulation housing 172, a powered articulation switch 174, anarticulation motor 132 and a manual articulation knob 176. Translationof the powered articulation switch 174 or pivoting of the manualarticulation knob 176 activates the articulation motor 132 which thenactuates an articulation gear 233 of the articulation mechanism 170 asshown in FIG. 4. Actuation of articulation mechanism 170 causes the endeffector 160 to move from its first position, where longitudinal axisB-B is substantially aligned with longitudinal axis A-A, towards aposition in which longitudinal axis B-B is disposed at an angle tolongitudinal axis A-A. The powered articulation switch 174 may alsoincorporate similar non-linear speed controls as the clamping mechanism.These can be controlled by the switches 114 a and 114 b.

With reference to FIGS. 2 and 3, the housing 110 includes switch shields169 having a wing-like shape and extending from the top surface of thehousing 110 over the switch 174. The switch shields 169 preventaccidental activation of the switch 174 and require the user to reachbelow the shield 169 in order to activate the articulation mechanism170.

Additionally, articulation housing 172 and powered articulation switch174 are mounted to a rotating housing assembly 180. Rotation of arotation knob 182 about first longitudinal axis A-A causes housingassembly 180 as well as articulation housing 172 and poweredarticulation switch 174 to rotate about first longitudinal axis A-A, andthus causes corresponding rotation of distal portion 224 of firing rod220 and end effector 160 about first longitudinal axis A-A. Thearticulation mechanism 170 is electro-mechanically coupled to one ormore conductive rings that are disposed on a housing nose assembly 155(FIG. 4). The conductive rings may be soldered and/or crimped onto thenose assembly 155 and are in electrical contact with a power source 300thereby providing electrical power to the articulation mechanism 170.The nose assembly 155 may be modular and may be attached to the housing110 during assembly to allow for easier soldering and/or crimping of therings. The articulation mechanism 170 may include one or more brushand/or spring loaded contacts in contact with the conductive rings suchthat as the housing assembly 180 is rotated along with the articulationhousing 172 the articulation mechanism 170 is in continuous contact withthe conductive rings thereby receiving electrical power from the powersource 300.

Further details of articulation housing 172, powered articulation switch174, manual articulation knob 176 and providing articulation to endeffector 160 are described in detail in commonly-owned U.S. patentapplication Ser. No. 11/724,733 filed Mar. 15, 2007, the contents ofwhich are hereby incorporated by reference in their entirety. It isenvisioned that any combinations of limit switches, proximity sensors(e.g., optical and/or ferromagnetic), linear variable displacementtransducers and shaft encoders which may be disposed within housing 110,may be utilized to control and/or record an articulation angle of endeffector 160 and/or position of the firing rod 220.

As shown in FIG. 4, the instrument 10 also includes a microcontroller400 electrically coupled to the motor 200 and various sensors disposedin the instrument 10. The sensors detect various operating parameters ofthe instrument 10 (e.g., linear speed, rotation speed, articulationposition, temperature, battery charge, and the like), which are thenreported to the microcontroller 400. The microcontroller 400 may thenrespond accordingly to the measured operating parameters (e.g., adjustthe speed of the motor 200, control articulation angle, shut-off thepower supply, report error conditions, etc.).

With reference to FIGS. 4-6, the articulation mechanism 170 housedwithin the articulation housing 172 is shown, which includes thearticulation knob 176, an articulation spindle 250, and an articulationlink 252 (FIG. 6). The articulation spindle 250 is rotatably housedwithin the articulation housing 172 and provides a mechanical interfacebetween the articulation knob 176 and the articulation link 252 thatinterfaces with the end effector 160 to impart articulation thereto. Thearticulation spindle 250 includes a cylindrical member 254 and a flange260 disposed on top of the cylindrical member 254 (See FIG. 6). Theflange 260 includes the articulation gear 233 and extends laterally fromthe cylindrical member 254 and has a diameter, which is larger than thediameter of the cylindrical member 254. The articulation gear 233 iscoupled to the articulation motor 132, which provides powered orassisted articulation of the end effector 160.

The articulation knob 176 is mounted on top of the articulation spindle250. This allows for rotational motion of the articulation knob 176 tobe translated to the rotational motion of the articulation spindle 250.The longitudinal motion of articulation link 252 is imparted via therotational motion of the articulation spindle 250. The articulation link252 mechanically interfaces with the articulation spindle 250 via a linkinterface member 262 which extends downwardly from a bottom surface ofthe articulation spindle 250. The articulation link 252 includes anarticulation slot 264 which extends laterally across the articulationlink 252. The interface member 262 is positioned off center on thebottom surface of the cylindrical member and is received within the slot264. During rotation of the articulation spindle 250, the interfacemember 262 is rotated around the center thereof. Since the slot 264 isdimensioned at its width to substantially fit around the interfacemember 262, the interface member 262 only travels in a lateral directiontherein and the longitudinal component of the rotational motion of theinterface member 262 is translated to the articulation link 252.

With reference to FIGS. 7-9, the instrument 10 includes an articulationsensor assembly 302 having a photo sensor 268 disposed over (e.g.,facing) the articulation link 252. The photo sensor 268 emits a lighttoward the articulation link 252 and measures properties of thereflected light. The articulation link 252 includes a marker 270 (FIG.9), which may be a non-reflective mark (e.g., a slot) or a highlyreflective mark (e.g., mirrored surface, polished metal, etc.). As shownin FIG. 9, the marker 270 is positioned on the articulation link 252such that the marker 270 is disposed opposite the photo sensor 268, whenthe articulation link 252 is at an unarticulated position. Theunarticulated position corresponds with the end effector 160 is at anangle of 0° (e.g., aligned with the body portion 168). The photo sensor268 continually measures the light reflected from the articulation link252 as the articulation link 252 is moved in the distal direction, whenthe articulation link 252 is withdrawn to the unarticulated position,the reflected light is modified by the marker 270 (e.g., almost fullyreflected or passes therethrough). This allows the photo sensor 268 tomeasure the 0° position. The photo sensor 268 is coupled to themicrocontroller 400 and is configured to transmit a sensed signalcorresponding to the changes in the reflected light due to articulationto the microcontroller 400. The microcontroller 400 then determines thearticulation angle based on the light measurements transmitted by thephoto sensor 268, since the measurements correspond to the displacementof the articulation link 252.

In another embodiment, shown in FIG. 7, the articulation sensor assembly302 includes a photo emitter 272 and a photo receiver 274 arrangedopposite each other on the opposite sides of the articulation link 252.The photo emitter 272 supplies a beam of light toward the photo receiver274 through the marker 270 when the end effector 160 is at the 0°position. As the articulation link 252 is moved in the distal direction,the marker 270 moves away from the photo emitter 272 and the photoreceiver 274 and the articulation link 252 thereby interrupts the beamof light therebetween. The photo sensor 268 and the photo emitter 272may emit light at any suitable wavelength (e.g., visible spectrum,infrared, etc.).

FIG. 10 illustrates another embodiment of the articulation sensorassembly 302 that includes a magnetic sensor 276 (e.g., Hall-effectsensor) disposed in the articulation housing 172. The sensor 276 isdisposed opposite a magnet 278 that is enclosed or otherwise attached tothe articulation knob 176. The sensor 276 and the magnet 278 are alignedwith respect to each other when the articulation knob 176 is centeredand the end effector 160 is at the 0° position. As the articulation knob176 is rotated to articulate the end effector 160, the magnet 278 ismoved from the sensor 276 which correlates the absence and/or decreasein the magnetic field with the articulation of the end effector 160.When the articulation knob 176 is returned to the centered position, themagnet 278 and the sensor 276 are realigned and the sensor 276determines that the end effector 160 is at the 0° position. The sensor276 is coupled to the microcontroller 400 and is configured to transmita sensor signal reflective of the changes in the magnetic field due tothe articulation to the microcontroller 400. The microcontroller 400then determines the articulation angle based on the magnetic fieldchanges as transmitted by the sensor 276, since the measurements arereflective of the articulation of the end effector 160.

FIG. 10 also illustrates another embodiment of the articulation sensorassembly 302 that includes a sensor switch 280 disposed on thearticulation housing 282. The switch 280 is disposed opposite aprotrusion 282 that is attached to the articulation knob 176. The switch280 and the protrusion 282 are aligned with respect to each other whenthe articulation knob 176 is centered and the end effector 160 is at the0° position. As the articulation knob 176 is rotated to articulate theend effector 160, the protrusion 282 is moved from the switch 280 andthe switch 282 is deactivated. When the articulation knob 176 isreturned to the centered position, the protrusion 282 and the switch 280are realigned and the switch 280 is activated which denotes that the endeffector 160 is at the 0° position. The switch 280 is coupled to themicrocontroller 400 and is configured to transmit the sensor signalreflective of the articulation knob 176 being at the 0° position. Themicrocontroller 400 then determines that the end effector 160 is in anunarticulated position.

FIG. 10 shows another embodiment of the articulation sensor assembly 302having a potentiometer 290 disposed on the articulating link 252. Thepotentiometer 290 is electrically coupled to a contact 292. The contact292 slides along the surface of the potentiometer 290 as thearticulation link 252 is moved in the distal direction due to therotation of the articulation knob 176. As the contact 292 slides acrossthe potentiometer 290 the position of the contact 292 along thepotentiometer 290 adjusts accordingly. The distance the contact 292moves along the potentiometer 290 is proportional to the degree ofarticulation of the end effector 160. An initial position of the contact292 corresponds to the 0° position of the end effector 160. Thepotentiometer 290 also allows for tracking of the exact angle ofarticulation.

The potentiometer 290 may also be disposed in a rotational configurationabout the spindle 254 allowing the contact 292 to track rotationalposition of the spindle 254. The contact 292 is aligned at apredetermined position with respect to the potentiometer 290 thatcorresponds to the 0° position of the end effector 160, allowing thecontact 292 to determine the articulation angle of the end effector 160.In one embodiment, the potentiometer 290 may be disposed in indirectcontact with the articulation link 252 and/or the articulation spindle254, such as, via gearing. The potentiometer 290 is coupled to themicrocontroller 400 and is configured to transmit a sensor signalreflective of the changes in the electric current due to the rotation ofthe spindle 254 or displacement of the articulation link 252 to themicrocontroller 400. The microcontroller 400 then determines thearticulation angle based on the electrical current changes astransmitted by the potentiometer 290, since the measurements arereflective of the articulation of the end effector 160.

In another embodiment, as shown in FIG. 11, the articulation sensorassembly 302 includes an optical encoder sensor 293. The encoder sensor293 includes a linear or rotary encoder 294 and a combination of a photoemitter 296 and a photo receiver 298 arranged opposite each other on theopposite sides of the encoder 294. The photo emitter 296 and receiver298 are configured to determine the number of interruptions in a lightbeam which is continuously provided therebetween. As the encoder 294 istranslated linearly or rotatably with the articulation of the endeffector 160, the photo emitter 296 and emitter 298 measure the numberof interruptions in the light beam and rate of occurrences thereof,which allow for determination of the articulation angle of the endeffector 160 based on the displacement of the articulation link 252 orthe articulation spindle 254. The encoder sensor 293 converts motioninto a sequence of digital pulses. By counting a single bit or bydecoding a set of bits, the pulses can be converted to relative orabsolute position measurements. The encoder sensor 293 is coupled to themicrocontroller 400 and is configured to transmit a sensor signalreflective of the motion of the spindle 254 or of the articulation link252 to the microcontroller 400. The microcontroller 400 then determinesthe articulation angle based on the electrical current changes astransmitted by the potentiometer 290, since the measurements arereflective of the articulation of the end effector 160.

It will be understood that various modifications may be made to theembodiments shown herein. Therefore, the above description should not beconstrued as limiting, but merely as exemplifications of preferredembodiments. Although specific features of the powered surgicalinstrument are shown in some of the drawings and not in others, this isfor convenience only as each feature may be combined with any or all ofthe other features in accordance with the aspects of the presentdisclosure. Other embodiments will occur to those skilled in the art andare within the following claims.

1-19. (canceled)
 20. A surgical instrument, comprising: a handleportion; a body portion extending distally from the handle portion anddefining a first longitudinal axis; an articulation tool assemblydefining a second longitudinal axis and having a proximal end, thearticulation tool assembly disposed at a distal end of the body portionand being movable from a first position in which the second longitudinalaxis is substantially aligned with the first longitudinal axis to atleast a second position in which the second longitudinal axis isdisposed at an angle with respect to the first longitudinal axis; anarticulation mechanism configured to articulate the articulation toolassembly, the articulation mechanism including: an articulation linkmechanically engaged to the articulation tool assembly; and anarticulation knob mechanically engaged to the articulation link, whereinrotational motion of the articulation knob is translated intoarticulation movement of the articulation tool assembly through thearticulation link; and an articulation sensor assembly including: aphoto sensor disposed in spaced relation to the articulation link andconfigured to detect light reflected from the articulation link, thephoto sensor configured to transmit a sensor signal; and amicrocontroller configured to determine an articulation angle of thearticulation tool assembly based on the sensor signal.
 21. The surgicalinstrument according to claim 20, wherein the microcontroller isconfigured to determine the articulation angle as a function of adisplacement of the articulation link based on the reflected light. 22.The surgical instrument according to claim 20, wherein the articulationlink includes a marker at a location that corresponds with anunarticulated position of the articulating surgical tool assembly whenthe marker is disposed over the photo sensor.
 23. A surgical instrument,comprising: a handle portion; a body portion extending distally from thehandle portion and defining a first longitudinal axis; an articulationtool assembly defining a second longitudinal axis and having a proximalend, the articulation tool assembly disposed at a distal end of the bodyportion and being movable from a first position in which the secondlongitudinal axis is substantially aligned with the first longitudinalaxis to at least a second position in which the second longitudinal axisis disposed at an angle with respect to the first longitudinal axis; anarticulation mechanism configured to articulate the articulation toolassembly, the articulation mechanism including: a housing; and anarticulation knob moveable relative to the housing and mechanicallyengaged to the articulation tool assembly, wherein rotational motion ofthe articulation knob is translated into articulation movement of thearticulation tool assembly; and an articulation sensor assemblyincluding: a magnet coupled to the articulation knob and a magneticsensor coupled to the housing, the magnetic sensor configured to measurea magnetic field of the magnet and transmit a sensor signal; and amicrocontroller configured to determine an articulation angle of thearticulation tool assembly based on the sensor signal.
 24. The surgicalinstrument according to claim 23, wherein the microcontroller isconfigured to determine the articulation angle as a function of adisplacement of the articulation knob based on the magnetic field. 25.The surgical instrument according to claim 23, further comprising aswitch coupled to the housing, the switch configured to actuate when thearticulation tool assembly is in at least one of the first position orthe second position.
 26. The surgical instrument according to claim 25,wherein the microcontroller receives a switch signal from the switch andis configured to determine whether the articulation tool assembly is inthe first position based on the switch signal.
 27. A surgicalinstrument, comprising: a handle portion; a body portion extendingdistally from the handle portion and defining a first longitudinal axis;an articulation tool assembly defining a second longitudinal axis andhaving a proximal end, the articulation tool assembly disposed at adistal end of the body portion and being movable from a first positionin which the second longitudinal axis is substantially aligned with thefirst longitudinal axis to at least a second position in which thesecond longitudinal axis is disposed at an angle with respect to thefirst longitudinal axis; and an articulation mechanism configured toarticulate the articulation tool assembly, the articulation mechanismincluding: an articulation link mechanically engaged to the articulationtool assembly, the articulation link including a contact disposedthereon; and an articulation knob mechanically engaged to thearticulation link, wherein rotational motion of the articulation knob istranslated into articulation movement of the articulation tool assemblythrough the articulation link; and an articulation sensor assemblyincluding: a potentiometer electrically coupled to the contact of thearticulation link and configured to measure an electrical currentthrough the contact and transmit a sensor signal; and a microcontrollerconfigured to determine an articulation angle of the articulation toolassembly based on the sensor signal.
 28. The surgical instrumentaccording to claim 27, wherein the microcontroller is configured todetermine the articulation angle as a function of a displacement of thearticulation link based on the electrical current.
 29. The surgicalinstrument according to claim 27, further comprising a switch coupled tothe housing, the switch configured to actuate when the articulation toolassembly is in at least one of the first position or the secondposition.
 30. The surgical instrument according to claim 29, wherein themicrocontroller receives a switch signal from the switch and isconfigured to determine whether the articulation knob is in the firstposition based on the switch signal.